Cool, but not enough variance
I liked the beginning part a lot. It has a very cool ambient and dark style to it. Reminds me of some of the dark ambient songs in the Half Life 2 and Portal soundtrack (which I love, so nice job!).
But the rest of the song didn't really go anywhere.
The drums where kind of cool, but they put a halt on the cool atmosphere you had going. It would have been ok if there where some more changes to the chords and some subtle harmonies coming in. But sticking with the same chords and beat the whole way through makes it feel like it doesn't go anywhere.
I do like some of the style though. And if you try out some different song structures and develop the ideas a bit more you could have some pretty nice stuff.
This could easily be a song that gets left on loop for ages without noticing and hypnotizes you, but there'd need to be more to break it up, so it doesn't feel like one 10 second loop over and over with a lead synth on top.